The well known railway car airbrake system, as developed from the Westinghouse airbake, has basically been an all pneumatically operated brake system. Recently, however, various improvements have been incorporated in the brake system which improvements involve the use of electrical pressure sensors, electrically controlled valves, etc.
For example, the modern brake system may have an end-of-train unit which may open or close valves to exhaust brakepipe pressure for a service brake application or an emergency brake application. An end-of-train unit has one or more transducers for measuring the brakepipe air pressure. An end-of-train unit may be connected for communication with the lead locomotive by way of a radio link or by trainline cables which are connected from railway car to railway car along the length of the train.
As is well known, transducers which convert a pressure signal into an electrical signal are available in two general types. One type is for mounting on a housing and includes a cylindrical body and a male pipe fitting concentric with the axis of the cylindrical body. Such male pipe fitting is threaded into the housing by rotation about its axis and is sealed, to prevent air loss, by a sealant placed on the pipe threads. These prior art transducers generally have a length that is greater than their diameter and they require a significant amount of space.
Another type of transducer is produced in the form of a low profile rectangular block. This transducer is normally mounted flat on a panel by screws. It has a male pipe fitting which fits through a hole on the panel, so that a hose having a female pipe fitting on its end may be attached to it. In an environment having relatively limited space, this type of prior art transducer may not be able to be mounted on a housing because it needs to be rotated to be connected and its rectangular form could interfere with nearby components.